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Commit 80a0a1a9 authored by Matthew Wilcox's avatar Matthew Wilcox
Browse files

xarray: Extract entries from an XArray 



The xa_extract function combines the functionality of
radix_tree_gang_lookup() and radix_tree_gang_lookup_tagged().
It extracts entries matching the specified filter into a normal array.

Signed-off-by: default avatarMatthew Wilcox <willy@infradead.org>
parent b803b428

include/linux/xarray.h

+2 −0
Original line number Diff line number Diff line
@@ -284,6 +284,8 @@ void *xa_find(struct xarray *xa, unsigned long *index, 
		unsigned long max, xa_mark_t) __attribute__((nonnull(2)));

void *xa_find_after(struct xarray *xa, unsigned long *index,

		unsigned long max, xa_mark_t) __attribute__((nonnull(2)));

unsigned int xa_extract(struct xarray *, void **dst, unsigned long start,

		unsigned long max, unsigned int n, xa_mark_t);



/**

 * xa_init() - Initialise an empty XArray.

lib/xarray.c

+80 −0
Original line number Diff line number Diff line
@@ -1444,6 +1444,86 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp, 
}

EXPORT_SYMBOL(xa_find_after);



static unsigned int xas_extract_present(struct xa_state *xas, void **dst,

			unsigned long max, unsigned int n)

{

	void *entry;

	unsigned int i = 0;



	rcu_read_lock();

	xas_for_each(xas, entry, max) {

		if (xas_retry(xas, entry))

			continue;

		dst[i++] = entry;

		if (i == n)

			break;

	}

	rcu_read_unlock();



	return i;

}



static unsigned int xas_extract_marked(struct xa_state *xas, void **dst,

			unsigned long max, unsigned int n, xa_mark_t mark)

{

	void *entry;

	unsigned int i = 0;



	rcu_read_lock();

	xas_for_each_marked(xas, entry, max, mark) {

		if (xas_retry(xas, entry))

			continue;

		dst[i++] = entry;

		if (i == n)

			break;

	}

	rcu_read_unlock();



	return i;

}



/**

 * xa_extract() - Copy selected entries from the XArray into a normal array.

 * @xa: The source XArray to copy from.

 * @dst: The buffer to copy entries into.

 * @start: The first index in the XArray eligible to be selected.

 * @max: The last index in the XArray eligible to be selected.

 * @n: The maximum number of entries to copy.

 * @filter: Selection criterion.

 *

 * Copies up to @n entries that match @filter from the XArray.  The

 * copied entries will have indices between @start and @max, inclusive.

 *

 * The @filter may be an XArray mark value, in which case entries which are

 * marked with that mark will be copied.  It may also be %XA_PRESENT, in

 * which case all entries which are not NULL will be copied.

 *

 * The entries returned may not represent a snapshot of the XArray at a

 * moment in time.  For example, if another thread stores to index 5, then

 * index 10, calling xa_extract() may return the old contents of index 5

 * and the new contents of index 10.  Indices not modified while this

 * function is running will not be skipped.

 *

 * If you need stronger guarantees, holding the xa_lock across calls to this

 * function will prevent concurrent modification.

 *

 * Context: Any context.  Takes and releases the RCU lock.

 * Return: The number of entries copied.

 */

unsigned int xa_extract(struct xarray *xa, void **dst, unsigned long start,

			unsigned long max, unsigned int n, xa_mark_t filter)

{

	XA_STATE(xas, xa, start);



	if (!n)

		return 0;



	if ((__force unsigned int)filter < XA_MAX_MARKS)

		return xas_extract_marked(&xas, dst, max, n, filter);

	return xas_extract_present(&xas, dst, max, n);

}

EXPORT_SYMBOL(xa_extract);



#ifdef XA_DEBUG

void xa_dump_node(const struct xa_node *node)

{